Striving to compete with front-runner J.R. Martinez -- who struggled with an ankle injury this week -- Kardashian went into the routine confident that luck was on his side.

"In the past, I've gotten points off for sticking my butt out, but in the samba, it's a lot of hip action and booty shaking," he reasoned before hitting the floor with pro Cheryl Burke. "Apparently, my butt is my secret weapon in the samba. I feel like I'm in the perfect position now."

Performing the routine -- his first out of three -- as stepdad Bruce Jenner, mom Kris and sister Kourtney (with son Mason and boyfriend Scott Disick) looked on, the reality star did his best to nail his footwork, but all judge Carrie Ann Inaba could pay attention to was his famous backside.

"Holy cow, that was bootylicious," Inaba raved after Kardashian, 24, performed the lively Latin number with Burke. "Who are you? What was that?!"

Kardashian's hip action also easily impressed Bruno Tonioli, who said Kardashian was "exceeding all expectations. That's how you turn a handicap into an asset. Keep using your butt," he told the celeb dancer, who earned his highest score of the competition thus far, 28 points out of 30.

As the night went on, Kardashian continued to play to his strengths, in an Argentine tango and a Cha Cha relay dance.

Ending the night with a total score of 65 out of 70 points, Kardashian found himself in second place on the semi-final leaderboard. Ricki Lake managed to beat out Kardashian by a mere two points, while Martinez finished with 56, and Hope Solo just 49.

Tell Us: Should Rob's booty shaking earn him a place in next week's finals?